Vista - rename problem

I have Vista SP1

Here is a directory listing:

Volume in drive E is 250GB USB
Volume Serial Number is 109F-6BD0

Directory of E:\test

10/04/2008 16:05 <DIR> .
10/04/2008 16:05 <DIR> ..
26/03/2008 13:57 7,752,223 1.mp3
26/03/2008 13:57 7,311,195 2.mp3
26/03/2008 13:57 8,029,040 3.mp3
26/03/2008 13:57 8,208,763 4.mp3
26/03/2008 13:57 8,046,804 5.mp3
26/03/2008 13:57 9,614,151 6.mp3
6 File(s) 48,962,176 bytes
2 Dir(s) 79,119,037,440 bytes free

I now do a bulk rename of the files (highlight all, rename first file in
list to song (01)):

Volume in drive E is 250GB USB
Volume Serial Number is 109F-6BD0

Directory of E:\test

10/04/2008 16:07 <DIR> .
10/04/2008 16:07 <DIR> ..
26/03/2008 13:57 9,614,151 song (01).mp3
26/03/2008 13:57 7,752,223 song (2).mp3
26/03/2008 13:57 7,311,195 song (3).mp3
26/03/2008 13:57 8,029,040 song (4).mp3
26/03/2008 13:57 8,208,763 song (5).mp3
26/03/2008 13:57 8,046,804 song (6).mp3
6 File(s) 48,962,176 bytes
2 Dir(s) 79,119,037,440 bytes free


As you can see, 1.mp3 is not renamed song (01). This is completely
reproducable. Any ideas? This behaviour does not happen on XP.